Solution Concentration
Read 281 – 283. Try questions 1 – 8 (show work)
Concentration = quantity of solute
quantity of solution (not solvent)
There are 3 basic ways to express concentration:
1) percentages, 2) very low concentrations,
and 3) molar concentrations
1) % concentration can be in V/V, W/W, or W/V
• Like most %s, V/V and W/W need to have the
same units on top and bottom.
• W/V is sort of in the same units; V is mostly
water and water’s density is 1 g/mL or 1 kg/L
3 g H2O2/100 mL solution ≈ 3 g H2O2/100 g solution
Solution Concentration
More practice
2) Expressing concentrations in parts per million
(ppm) requires the unit on top to be 1,000,000
times smaller than the unit on the bottom
E.g. 1 mg/kg or μg/g
• Multiples of 1000 are expressed in this order
μ_, m_, _, k_ (“_” is the base unit) (pg.631)
• Notice that any units expressed as a volume
must be referring to a water solution (1L = 1kg)
• For parts per billion (ppb), the top unit would
have to be 1,000,000,000 times smaller
3) Molar concentration is the most commonly
used in chemistry. Ensure that units are mol/L.
1. What is the % W/W of copper in an alloy when
10 g of Cu is mixed with 250 g of Zn?
2. What is approximate % V/V if 30 mL of pure
ethanol is added to 250 mL of water?
3. What is the % W/W if 8.0 g copper is added to
enough zinc to produce 100 g of an alloy?
Read 284 – 287. Do Q 11 – 17 (show work)